Previous studies have shown that the genetic spontaneously hypertensive rats incorporate lysine into non-collagen protein of the mesenteric arteries at a greater rate than do age matched control animals. We have now also observed this phenomenon in the spermatic and testicular arteries. Using these arteries as being typical of small resistance vessels we have examined the effect of antihypertensive agents on this parameter of vascular protein metabolism. In general drugs that prevent or reduce sympathetic nerve input to the tissue tend to normalize the enhanced vascular incorporation of lysine into non-collagen protein in the spontaneously hypertensive rat. These agents include hexamethonium, clonidine, and phenoxybenzamine. Conversely hydralazine which is an effective antihypertensive agent in these animals did not affect this parameter. Of interest is the observation that the beta-blocker, propranolol, neither reduced blood pressure or changes amino acid incorporation in these hypertensive rats. Our data are consistent with the concept that the sympathetic nervous system exerts a trophic effect on vascular non-collagen protein synthesis. BIBLIOGRAPHIC REFERENCES: Lovenberg, W., Yamabe, H., Nakada, T. and Yamori, Y.: Vascular protein synthesis in the spontaneously hypertensive rat. In: Spontaneous Hypertension: its Pathogenesis and Complications (Proceedings on the Second International Symposium on the Spontaneously Hypertensive Rat), 1977, pp 56-60. Yamori, Y., Nakada, T., and Lovenberg, W.: Effect of antihypertensive therapy on lysine incorporation into vascular protein of the spontaneously hypertensive rat. European J. Pharmacology 38: 349-355, 1976.